HN Theater @HNTheaterMonth

⬐ Jimmc414

Interesting link regarding Trebuchet Mechanics http://www.algobeautytreb.com/trebmath356.pdf

⬐ grondilu

He calls it a trebuchet but I'd call it a slingshot.

In any case, a very cool project IMHO. I've long wondered how fast modern technology could throw a projectile without resorting to explosives. I now know it can at least be supersonic.

Can it go even faster, though? Is there an even better mechanical design than a slingshot?

⬐ polishdude20

My understanding is a trebuchet operates using some heavy weight. This is more of a slingshot with an arm attached.

⬐ jaclaz

It is not easy to "classify" this kind of devices, you are thinking of the (more common) "counterweight trebuchet", but there were other kinds of trebuchets, propelled by (direct or indirect) traction or by torsion (similarly to the ballista).

https://en.wikipedia.org/wiki/Trebuchet

https://exarc.net/issue-2018-3/at/traction-trebuchet

This seems like a form of traction trebuchet with traction provided by the elastic.

⬐ mjh2539

It depends on the weight and ballistic coefficient of the projectile and the medium through which the projectile travels (as far as "muzzle" velocity goes). Using compressed air and a small enough projectile you get well over 1400 feet per second/ 425 meters per second. Using helium you can get it a little higher. That's about on par than what the guy in the youtube video achieved.

Railguns can get projectiles up to mach 8. The magnets at the HLC can get particles pretty close to the speed of light.

I think if you continued with the trebuchet/rubberband approach you'd really only be limited by the amount of tension you'd be able to put your band under. There are probably better materials than rubber.

⬐ grondilu

I don't think the rubber is the limiting factor. You can always use more rubber.

I think the main stopper for higher speeds would be materials strength, especially with that design relying on a cable, but even so I doubt the limits are anywhere close from what was achieved in this video.

There's some similarities with the supersonic trebuchet to these ideas, in terms of engineering.

Mach 33 is needed to escape orbit, so if you were going to launch a ball bearing into space, you'd need something at least 33 times more powerful than the rubber bands and 2x4 trebuchet.

https://youtu.be/gdXOS-B0Bus

It'd be interesting to run through those parameterizations with assumptions scaled to maximize a payload for reaching orbit using things like modern high strength steel and mechanical advantage and so on. It seems possible.

The amount of energy involved is terrifying - a space launch trebuchet would also be an anti-tank trebuchet.

⬐ feoren

> a space launch trebuchet would also be an anti-tank trebuchet

There are much easier ways to destroy a tank than a 20-billion-dollar centrifuge.

⬐ bee_rider

Few with such spectacular failure modes, though.

⬐ robbedpeter

To quote one of my favorite movies, "big bada boom."

⬐ robbedpeter

Riffing off the $200 plywood and rubber band supersonic trebuchet was where I was going - e.g. if you used higher quality materials and a few thousand dollars, could you launch a 1kg steel ball into orbit? A 500g payload? Could you use ceramics for ablative shielding designed to break open in orbit, hatching a useful cubesat type device?

The idea of hobbyist level engineering achieving orbital escape velocities is the scary bit.

The design space equations used by the trebuchet guy could answer the questions, I think.

I’d like to suggest linking directly to the video (https://www.youtube.com/watch?v=gdXOS-B0Bus) instead of the hackaday page, which doesn’t even pretend to add anything and is largely incoherent besides.

⬐ sbierwagen

Direct link to the timestamp of first full power shot: https://youtu.be/gdXOS-B0Bus?t=806

Second shot: https://youtu.be/gdXOS-B0Bus?t=871

⬐ jacquesm

Hackaday is just blogspam. They happily rip off your work.

⬐ AceJohnny2

On the other hand, I would never have heard of any of the cool projects they feature if not for Hackaday. Do you know of better aggregators for such content?

⬐ thesmok

You're not accounting for all the high quality content they produce. Like Creating a PCB in Everything, or Logic Noise.

https://hackaday.com/tag/logic-noise/

https://hackaday.com/tag/creating-a-pcb-in-everything/

⬐ agumonkey

they also have a kind of community website full of maniacs (in the good hacker sense)

people making discrete custom CPUs for instance

I admit I don't like hackaday a lot but they have some value

⬐ fho

They've been bought out some years ago, before that it was mostly just interesting articles at a much lower rate.

⬐ agumonkey

A sad but regular occurence of business mindset.. quantity .. quality and the usual.

⬐ ok_dad

I agree this is a bad textual article, but am I one of the few people who prefer text and images over video? I literally never watch a video link here but I'll read almost any textual content. Not judging others, but I'm sad that technical videos are so prevalent and most don't have any textual counterpart.

⬐ andrewaylett

The text was sufficient to prompt me to watch the video, which I wouldn't otherwise have done.

⬐ jacquesm

The video is very good, actually, for once.

⬐ rhn_mk1

I hope the paper that was explained in the video is available published somewhere.

⬐ leephillips

I absolutely prefer text to video for tutorials or documentation. I don‘t think this preference is unusual. But the linked article is not a text version of the video. It has, in fact, no content. Everything is in the video. And the final bit, where you hear the snap of the sonic boom, is worth watching the whole thing.

⬐ ok_dad

Agreed, thanks for responding. I guess it was more bitching than I should have done and off topic here; I agree with your assessment of this "article".